For more than a decade, the Affordable Care Act has been the Republican Party’s nemesis. As it was first debated in Congress in 2009, when it was enacted in 2010 and through the next six years of implementation, Republican leaders rallied supporters by vociferously opposing it and calling for repeal. The Trump administration and states controlled by Republicans remain hostile to the ACA.

But the coronavirus pandemic’s fast-moving destruction has pushed Republicans to rely on Barack Obama’s signature law to respond to the crisis, even taking action to strengthen it. The law, as written, requires that Americans who have recently lost jobs and insurance coverage to be permitted to enroll in its insurance marketplace, and they are doing so in swelling numbers. Meanwhile, Republicans recently backed stimulus legislation that increased federal funding for a critical part of the ACA: Medicaid for lower-income people. And Trump administration regulators have used their authority to insist that insurance plans pay for coronavirus tests as an “essential health benefit” under the ACA — a Republican target in the past.

Our research shows that this about-face cannot be explained by the pandemic alone. The party’s rank-and-file — and many other Americans — have shifted to supporting the ACA and expanded government payments for health care. The pandemic is giving Republicans cover to follow changing public opinion.

Republicans have spent 10 years trying to kill the Affordable Care Act

In 2017, after Republicans won the White House and controlled both chambers of Congress, they came within one Senate vote of killing the law. Since then, the Trump administration has worked to weaken or potentially destabilize the law by approving state waivers from ACA Medicaid rules, shortening the annual enrollment period and certifying cheaper health plans with less adequate coverage than had been possible under the Obama administration. It has also joined legal challenges that would overturn the law outright.

After the ACA became law in 2010, Republican lawmakers were in sync with their rank-and-file in resisting it. At the time, public opinion followed a now-familiar pattern. Americans loved it or hated it based on where they “belonged” in rigid partisan groups that shared similar conservative or liberal mindsets. Each group either supported or opposed the ACA accordingly.

But that polarized pattern has weakened.

Our research shows how the ACA has fundamentally changed attitudes about health care

Starting in 2010, the year Obama signed the ACA into law, we surveyed a national random sample of 1,000 Americans, plus an oversample of 200 Americans ages 18 to 64 who live in households with incomes below $35,000. We have returned to those same people every two years since and asked them the same questions. This approach lets us see how individuals’ views change over time. The survey has been conducted by Abt Associates, and the data are weighted to be nationally representative.

Although Americans voiced increasing appreciation for the law’s specific benefits by late 2014, overall evaluations of the law remained divided by partisanship, as Democrats expressed support and Republicans expressed opposition. Even among those who benefited directly from the law — for example, because they gained insurance coverage, gained help paying for prescription drugs or benefited from subsidies to help them pay for insurance — many still opposed it because of their Republican partisanship, concern that taxes might increase, general distrust in government or all three.

Over the past few years, though, the ACA has changed opinions in several significant ways. First, as Americans have grown increasingly accustomed to the ACA’s benefits, they have become more supportive of the law overall, with the ranks of those who “strongly” or “somewhat” favor it growing by six percentage points between 2016 and 2018. Over the same period, intense opposition fell and support for repeal plummeted by nine percentage points, to the lowest point since the law was enacted. More respondents reported appreciation for how the ACA had given them more access to health care and how it was covering seniors’ prescription drugs, subsidizing private health insurance and allowing parents’ plans to cover their children until they were 26 years old. Partisanship is giving way to pragmatism.

Second, the ACA’s survival and success at distributing benefits led many Americans to feel more of what political scientists call “political efficacy.” Seeing that government policies had improved their lives, they became more confident that government would respond to people like them. Low-income people, for example, increased their disagreement with the statement “Public officials don’t care much what people like me think” from 28 percent in 2016 to 32 percent in 2018. Men’s disagreement grew from 30 to 35 percent over the same period. Americans also became more assured that they could participate effectively in politics, as evidenced by the increase in racial and ethnic minorities who agreed that “I consider myself well qualified to participate in politics,” from 64 percent in 2016 to 70 percent in 2018. Scholars have long known that an increased sense of efficacy encourages more people to get involved in politics. This proved true with the ACA.

Those individuals who came to think more positively about government also became more likely to get involved politically, increasing their intent to vote, as well as their level of activity in other political activities, including volunteering to work on a political campaign, contacting an elected official about issues that concern them or contributing money to a political organization or candidate. While other factors were also at work, increased political efficacy helped lead to high turnout in the 2018 elections.

Third, Republicans’ attempts to repeal the ACA in 2017 and 2018 inadvertently boosted popular support for the law. Rank-and-file Republicans became less willing to choose candidates based on how strongly they opposed the ACA, even while Democrats became more motivated to choose candidates based on how fully they supported it.

Americans will continue to demand health coverage even after the pandemic ends

In other words, as the ACA went to work for them, Americans increasingly supported it. That’s consistent with what scholars call “policy feedback,” meaning that policies, once established, can affect attitudes in ways that change politics going forward — for example, by changing the public’s views about issues, how much people get involved in politics and what they expect from their governments and representatives.

Some conservative advocates still push legal challenges to the ACA. But overall, Republican lawmakers, faced with the pandemic’s health-care crisis, have slowed or stopped their efforts to terminate benefits that voters have come to expect. The ACA, which extended health coverage to 20 million Americans, has become a first line of defense against the coronavirus pandemic, useful not only for individual medical care, but also for public health.

Lawrence R. Jacobs is the Mondale Chair for Political Studies and the McKnight Presidential Chair at the University of Minnesota’s Humphrey School of Public Affairs and Department of Political Science. He is the author of “Health Care Reform and American Politics: What Everyone Needs to Know,” New York, N.Y.: Oxford University Press, co-authored with Theda Skocpol.

Suzanne Mettler is the John L. Senior Chair of American Institutions in the Department of Government at Cornell University. Her most recent book is “Four Threats: The Recurring Crises of American Democracy,” co-authored with Robert C. Lieberman, forthcoming in August 2020 from St. Martin’s Press.

Ling Zhu is associate professor of political science at the University of Houston and the author of “Voices from the Frontline: Network Participation and Local Support for National Policy Reforms,” Journal of Public Administration Research and Theory, 2017, 27(2):284-300.